class Base{
    public Base(String s){
        System.out.print("B");
    }
}class X{
    Y y=new Y();
    public X(){
        System.out.print("X");
    }
}
class Y{
    public Y(){
        System.out.print("Y");
    }
}
//public class Derived extends Base{
//    public Derived (String s) {
//        //super(s);
//        System.out.print("D");
//    }
//    public static void main(String[] args){
//        new Derived("C");
//    }
//}